1. Field of the Invention
The present invention relates to pulse RF signals, and more particularly to an inexpensive method of measuring the RF carrier frequency of a stream of pulse RF signals in real-time or near real-time.
2. Description of Related Art
Radar and electronic counter measure (ECM) systems commonly employ pulse KF signals with narrow pulse widths and low duty cycles. Such pulses typically are generated by on/off switching (e.g. using a pin switch diode) of a continuous RF source, and can be of extremely short duration (100 nanoseconds). The frequency of an RF signal emitted by these systems is an important characteristic that must be accurately measured to assess a system's performance.
The conventional method for measuring RF frequency is to use expensive equipment such as electronic counters, spectrum analyzers, synchronous detectors and digital frequency discriminators, among others. The microwave counters EIP 1230A and 1231A manufactured by EIP Microwave, Inc. and the Hewlett Packard electronic counter HP 5361B are examples of instruments currently in use to measure RF pulse frequencies. These methods, however, do not provide the required frequency measurement accuracy for state-of-the-art radar and ECM systems. Electronic counters can provide only 500 Khz accuracy for a 100 ns pulse width signal. The spectrum analyzer accuracy for a 100 ns pulse width is typically 150 Khz. Additionally, electronic counters and spectrum analyzers are expensive, bulky, and require specialized hardware. Synchronous detectors are limited to 10 Khz measurement accuracy for a 100 ns pulse width signal while digital frequency discriminators can provide only 100 Khz measurement accuracy for a 100 ns pulse width signal. However, as the radar and ECM systems become more advanced, test technology must improve in order to assure the proper system performance.
Furthermore, in order to characterize the performance of a Unit Under Test (UUT) in an end-to-end test environment, one should not have to access the internal structure of the UUT
The present invention overcomes the aforementioned disadvantages.